Automatic work guidance mechanism

ABSTRACT

An apparatus for automatically guiding sheet material substantially in its own plane and relative to an operating zone by numerical control. The work, for instance a flexible fabric to be stitched in a sewing machine along a predetermined path, is moved in precise directional increments the X and Y components of which are imparted between tool strokes or needle insertions by coacting motive means in a non-rectilinear coordinate system. Low inertia is attained by a movable work supporting or clamping structure wherein a pivotal Y-arm carries a motor for moving an X-arm about its pivot, and the pivotal X-arm carries a motor for moving the work clamp and work radially relative to the X-arm pivot. A pulse generator coupled to the machine embodying the invention, illustratively a sewing machine devoid of conventional work feeding means such as a dog, provides multiple pulsing per revolution of a main crankshaft, and a pulse counting means signals each motor to yield an intermittent feed each controlled step of which is accelerated-decelerated between selective, variable dwells.

United States Patent 1 Schaefer, Jr. et al.

[ 1 AUTOMATIC WORK GUIDANCE MECHANISM [75] Inventors: llans F. Schaefer,Jr., Rockport;

Reade Williams, Hamilton, both of Mass.

[52] US. Cl ll2/l21.l2, 318/571, 318/696 [51] Int. Cl. D05b 21/00 [58]Field of Search ll2/l21.ll, 121.12,

[56] References Cited UNITED STATES PATENTS 3,015,806 l/1962 Wang et a1318/571 3,448,705 1/1969 Scherr et a]. ll2/l21.l2 3,474,747 10/1969Noiles 1l2/l2l.l2 3,579,279 5/1971 lnaba 318/696 3,585,478 6/1971Leenhouts 318/573 3,653,347 4/1972 Bianchi..... 112/l2l.12 3,656,3774/1972 Kosem 318/571 X 3,385,244 5/1968 Ramsey et al 112/102 X 3,528,3789/1970 Westolf; l12/l2l.15 3,405,670 10/1968 Scholl et a1. 1 12/102 X[451 July 3,1973

[ ABSTRACT An apparatus for automatically guiding sheet materialsubstantially in its own plane and relative to an operating zone bynumerical control. The work, for instance a flexible fabric to bestitched in a sewing machine along a predetermined path, is moved inprecise direc tional increments the X and Y components of which areimparted between tool strokes or needle insertions by coacting motivemeans in a non-rectilinear coordinate system. Low inertia is attained bya movable work supporting or clamping structure wherein a pivotal Y-armcarries a motor for moving an X-arm about its pivot, and the pivotalX-arm carries a motor for moving the work clamp and work radiallyrelative to the X-arm pivot. A pulse generator coupled to the machineembodying the invention, illustratively a sewing machine devoid ofconventional work feeding means such as a dog, provides multiple pulsingper revolution of a main crankshaft, and-a pulse counting means signalseach motor to yield an intermittent feed each controlled step of whichis accelerated-decelerated between selective, variable dwells.

2 Claims, 14 Drawing Figures \JATENTEDJUL 3 1975 SHKU 3 0f 5 PATEN IEOJUL 3 I975 'S NEEIUOFS 1 AUTOMATIC WORK GUIDANCE MECHANISM BACKGROUND OFTHE INVENTION This invention pertains to automatic mechanism forpositioning sheet material, especially flexible sheets of fabric or thelike, to be guided in programmed manner to and through the operatingzone of a machine. The invention is particularly well adapted for usewith a sewing machine which may be required to provide seams that arecurved as well as straight, but it will be understood that the inventionis not limited for use with a sewing machine, and that it also hasapplication in non-intermittently operative machines of many types andwherein a wide variety of sheet material including leather, paper, andplastics as well as fabric and nonwoven items are to be continuouslyguided in predetermined manner.

Prior attempts have been made to provide automatic means for relativelymoving a work piece and a tool for precisely operating thereon accordingto numerical control. Problems arise particularly when the work piece tobe processed is flexible or limp; edge guidance, for example, becomesinaccurate when a work margin is distorted or deflected. Also, sincework pieces of fabric or the like may be of low mass and even flimsywhile having quite irregular contour and curvature, it becomes essentialfor accurate results to employ guidance mechanism of low inertia andhigh response characteristics. Various earlier approaches employ a camshape.

for relatively guiding the work and tool thus necessitating a pluralityof interchangeable, massive, and costly cams if the machine is to doother than repeat operations. Another approach seeks, in an edge guidedautomatic sewing machine having a unidirectional feed dog, to employsensing means for properly rotating a work clamp about a needle axis,the clamp also being powered for movement along rectangular coordinatesrotatable with the clamped work. Also, photosensing means has beenemployed for controlling relative motion of a machine head and clothwork.

So far as known no prior automatic work positioning mechanism has provedcommercially acceptable for programmed operations on flexible sheetmaterial, presumably due to economic factors or inherentlyunsatisfactory performance such as may be attributed to ex ce ssinertia.

SUMMARY OF THE INVENTION In view of the foregoing it is an object ofthis invention to provide an improved, relatively economical apparatusfor relatively positioning flexible sheet material and a tool bynumerical control, the path of operation being precisely determined.

More specifically it is an object of this invention to provide a datacontrolled work positioning mechanism for obtaining high productivityand embodying a nonrectangular coordinate work moving means whereby aflexible sheet may be precisely moved in its own plane relative to anoperating tool, for instance a sewing machine needle.

A further object is to provide, especially for use with stitch formingmeans, an automatic system for predeterminedly shifting according tocontrol data a work piece directionally in its own plane betweensuccessive work engagements of the stitch forming means, the work motionto occur at variable rates between exactly known stitch receiving pointshaving substantially constant spacing.

In accordance with these objects and as herein shown, an automatic workpositioning apparatus eliminates the need for stitching skill byfeaturing a low inerrevolution of its crankshaft, i.e., 1,000 pulses perstitch.

The intermittent work clamp motion is the resultant of compensated X andY coordinate components imparted by their respective stepping motors,the latter being controlled from the same tape. For each selected groupof generated timing pulses counted, a pulse is sent to a stepping motor,then after a next selected group of counted synchronizer pulses asspecified in a table, another pulse is sent to the motor, etc. Thecontrol logic includes several such tables of different 7 lengthscalling for different numbers of stepping pulses to be sent to themotors, the tape or software indicating which table to use for eachmotor and picking-off desired stepping pulses for each stitch.

Inthe illustrative machine for peripheral operations on fabric the workclamp may be of selected contour for engaging the fabric within aboutone-fourth inch from a stitch line which may extend in any direction.The arrangement is desirably such that the control data determines oneor more of the following factors: start- BRIEF DESCRIPTION OF THEDRAWINGS The above and other features of the invention together withnovel details and combinations of parts will now be more particularlydescribed in connection with an illustrative embodiment, and withreference to the accompanying drawings thereof, in which:

FIG. 1 is a perspective and somewhat schematic view of automatic workguidance apparatus as applied to a sewing machine;

FIG. 2 is-a schematic diagram of the guidance control system indicatingits stepping motors shown in FIG. 1 and their control means;

FIG. 3 illustrates a magnified stitch length and indicates a typicaldistribution of zero work velocity as well as full velocity,acceleration and deceleration during the stitch making;

FIG. 4 is a diagram indicating theoretical derivation of a stitchlength;

FIG. 5 is a plan view of the apparatus shown in FIG. 1 having its workclamp mechanism loaded and guided for operating, for example, on a mansshirt collar;

FIG. 6 is a detail view of a presser foot as adapted to aid workguidance in any direction;

FIG. 7 is a view in front elevation and partly in section, on a largerscale, of the apparatus shown in FIG. 5, the sewing machine beingomitted and the relation of the work positioning motors to theircoordinate arms being indicated;

FIG. 8 is a section taken on the line VIII-VIII of FIG. 7 and showingthe pivotal relation of the coordinate arms and a portion of the workclamp mounting;

FIG. 9 is a section taken on the line IX-IX of FIG. 7 showing a motorconnecting means with a clamp moving rack;

FIG. 10 is a section taken on the line XX of FIG. 8 showing the workclamp and its mounting;

FIG. 11 is a plan view of the work clamp and a takeup means therefor;

FIG. 12 is a sectional detail taken on the line XII- -XII of FIG. 11;and

FIGS. 13 and 14 correspond largely to FIG. 8 and show an alternate workclamp structure in its inoperative and operative positions,respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention will be describedas applied to a stationary sewing machine generally designated 12 (FIGS.1, 2, 5) adapted to operate on fabric 14, it being understood that theinvention is not limited to sewing operations, nor to guidance of anyparticular sheet material. The apparatus embodying the invention couldalternatively be adapted for guidance movement of the machine relativeto a stationary work piece though such is not ordinarily preferred inview of the probably unfavorable inertia factor then encountered.

The machine 12 has stitch forming instrumentalities including atleastone vertically reciprocable needle 16 driven by the usual maincrankshaft (not shown) from a pulley-handwheel 18 by a power means (notshown). It may be assumed for present purposes that the crankshaft speedis constant.

The machine is secured on a work carrying table 20, and is not providedwith linear feeding means of conventional type, such as an orbital feeddog, but is adapted to operate in any direction on sheet material suchas the fabric collar 14 to be automatically guided substantially in itsown plane by numerically controlled mechanism which is hereinafter to bedescribed.

Before describing details of the work guidance structure as depicted inFIGS. 5-12, its mode of operation will be briefly explained withreference to FIGS. 1-4, it being assumed for simplicity that arectilinear coordinate arrangement isemployed, which is not strictly thecase. The work 14 is moved automatically by power means a constantstitch length Z between successive work penetrating strokes of theneedle 16, the variable X and Y components of each stitch beingpredetermined. For this purpose a pulse generating synchronizer 22 (FIG.2) coupled to the crankshaft as by a timing belt 24 running on thepulley 18 is adapted to provide in each revolution of the shaft l,000pulses. This is to say that for each stitch length Z the generatingsynchronizer 22 delivers 1,000 uniformpulses or 33,000 pulses per secondat 2,000 r.p.m. of the stitcher. A digital computer 26 showndiagrammatically only in FIG. 2 and programmed by softwear wear 28, forinstance a perforated tape (not shown), modulates the pulse frequencydelivered from the synchronizer 22 to control work acceleration anddeceleration between successive needle engagements or dwell intervals tobe dictated by stepping pulsing to a reversible X-motor 30 (FIGS. 1, 2,5 and 7) controlling change in radius and a reversible Y-motor 32 (FIGS.1, 2, 5 and 6. controlling change in angle.)

Referring further to FIG. 2, assuming a stitch of length Z as indicatedin FIGS. 3 and 4 to correspond with the 1,000 synchronizer pulses, thecomputer 26 is programmed to allot selected portions of each thousandpulses to the different feeding phases, namely and in order, dwell,acceleration, running speed, deceleration and dwell. Thus, for instance,control logic may count a first and a last 200 synchronizer pulses of astitch length Z as indicated in FIG. 2, allowing twofifths or 40 percentdwell time in a cycle for the needle 16, and between needle engagementscount or allocate 600 pulses percent) for work acceleration, full speedrunning, and deceleration, to the end that versatility and optimumperformance may be attained and minimum deviation forces created in thesystem to be explained. As schematically shown, for instance, thecomputer may divide, i.e., generate the intermediate 600 pulses, asrelates to Y or angular change motion, into a group A of 9 pulses foracceleration, another group B of 18 pulses for running, followed by agroup C of 9 for deceleration. The drive circuit 31 for the Y- motor 32is sent the acceleration pulse A after the initial, say 200, dwellpulses (0 in FIG. 3) have been counted, is sent the running pulse (B inFIG. 3) after 9 computer pulses are counted, is sent the deceleratingpulse (C in FIG. 3) after 18 more computer pulses etc. In like mannerthe computer 26 acting on the programmed tape information selecting atable of numbers corresponding to the mentioned 0, 9, l8, 9, 0 table,

sends similar pulsing to the drive circuit for the motor 30.I-Ience, asshown in FIG. 4 in feeding the work from a stitch point S (FIGS. 1, 2and 4) an incremental ramp length Z to any point C, the motors 30,32 arecaused to concurrently and proportionately, that is throughout the Zstep, transmit their respective components of motion, the componentsvarying-as required properly to locate C a Z distance from S. Velocityof the work, i.e., stitch speed and direction, is thus determinedprecisely between consecutive needle insertions.

Advantage ously, a presser foot 36 (FIGS. 6, 14) is adjustably mountedheightwise of the table 20 and is formed with an opening 38 coaxiallysurrounding the needle 16. This presser foot acts as a holddownregardless of the direction of work feed, the presser foot shank beingformed and disposed so as to allow a work clamp 52 to closely approachthe needle 16 from any side. As indicated in FIG. 14 the foot 36 ispreferably spaced slightly above thetable 20.

Referring now mainly to FIGS. 5-12 the automatic guidance mechanismhighly responsive to control data transmitted as just described will beexplained. A work moving means comprises a pair of cooperative,nonrectangular coordinate arms, namely an X-arm 40 on which the X-motor30 is secured, and a Y-arm 42 on which the Y-motor 32 is secured. TheX-arm 40 is pivotally secured to the table 20 by a pin 44 (FIGS. 1, 5)and the Y-arm 42 is pivotally secured to the table by a pin 46. Anoutput pinion 48 (FIG. 7) of the Y-motor 32 is accordingly effectivetoswing the X-arm 40 about the pin 44 in either direction, throughconnections about to be described, and an output pinion 50 (FIGS. 7 and9) of the X motor 30 is operative to move a work support, preferably inthe form of the clamp 52 (or 52 and a cooperative low friction plate 106later mentioned) radially relative to the axis of the X arm pivot pin44.

It is preferred to consider each feed increment Z as having X and Ycomponents though it will be recognized they are not strictlyorthogonal. This is due to the fact that the step of the motor 30actually imparts a small change in radius relative to the pivot 44 whilethe step of the motor 32 imparts a small change in angle, i.e., anarcuate path about the axis of that pivot; the resultant Z step is thecombination of two coordinate movements respectively small compared tothe effective lengths of the arms 40, 42, or the distance of the needle16 from their pivots 44, 46, respectively. Deviation from orthogonalrelation is accordingly insignificant in the illustrative systemembodying freedom in two degrees of movement.

For swinging the X-arm 40 the pinion 48 meshes with a rack 54 (FIGS. 7,l0 and 11) slidable lengthwise on spaced rollers 56 (FIG. 7) and 58(FIGS. 8, and 11) in guideways formed in the Y-arm 42, a front end ofthe rack being secured by means of an L-shaped bearing bracket 60 andtelescoping swivel pin 62 to the free end portion of the X-arm 40. Thepin 62 extends vertically in a bearing portion 64 integral with theX-arm 40 and is coupled to the bracket 60 by a lock pin 66 (FIGS. 8 and10).

For controlling radial movement of the work support or clamp 52 relativeto the X-arm pivot 44, the pinion 50 meshes with a rack 70 (FIGS. 7 and9) slidable in longitudinal guideways 72, 74 secured to the X-arm 40.Secured to an end of the rack 70 for horizontal movement therewith is awork clamp carrier 76 (FIGS. 8 and 11) and connections next to bedescribed. The carrier 76 is longitudinally guided by two spaced rollers78 journaled therein and rotatably engageable with inner walls of aguideway 80 connected to the underside of the X-arm 40. The carrier issecured to an upper U- shaped support 82 extending parallel to theX-arm. Pairs of parallel leaf springs 84, 84 and 86, 86 (FIG. 10) havingtheir respective upper ends riveted to the support 82 have their lowerends riveted to a Urshaped interengaging member 88 which is thusyieldingly suspended over the table between heightwise limits determinedby the lower or straddled leg of the support 82. The work clamp 52 isdetachably secured to the member 88 by spaced thumb screws 90, 90 (FIGS.8, 11 and 14) respectively threaded in holes 92, 92 shown in FIG. 10.The clamp 52 will normally have a bottom contour approximating the shapeof an article to be guided thereby and be of light weight. A s'indicatedherein the top clamp 52 has a cut-out friction pad 94 (FIG. 8)preferably of a shape and material to marginally engage with frictionthe upper surface of the work 14, the pad being secured as by adhesiveto the underside of the clamp 52.

As herein illustrated (see FIG. 11) an intermediate roller 96 in theguideway 80 is mounted to serve as a take-up for any front-rear play ofthe carrier 76 relative to the X-arm 40. For this purpose the roller 96is journaled in one end of a lever 98 pivoted by a pin 100 (FIGS. 7 andl 1) to the carrier 76. Between the pin 100 and the roller 96 a rubbergrommet 102 yieldable slightly in transverse shear, as shown in FIG. 12and interconnecting the lever 98 and the carrier 76 is effective to biasthe roller 96 in its guideway. Other alternative structure may of coursebe employed for this function if desired.

The clamp 52 and its pad 94 are automatically movable heightwise fromoperative guidance relation with a work piece 14 on the table 20 bymeans such as a solenoid (not shown) controlled from the perforatedprogram tape 28, the solenoid acting through a Bowden wire 104 (FIGS. 8,10, 13, 14) to elevate the member 88 and hence the pad 94 by deflectingthe springs 84, 84 and 86, 86 to the extent allowed by the support 82.Their descent into work engaging relation is by the influence of gravityplus force of the springs 84, 86.

For guidance of certain work pieces W it may be desirable to employ alower, thin work clamp 106 (FIGS. 13, 14) having a low friction undersurface. It is adapted slidably to engage the table 20 during operationand while holding the work flatly clamped against the underside of theclamp 52 or its pad 94. The clamp 106 is supported on parallel leafsprings 108 (one shown) secured to the member 88. Conveniently, when theclamp 52 is lifted as shown in FIG. 13, the work W may be placed betweenthe clamps 106 and 52. Desirably the contour of the low friction clamp106 may correspond in part to portions of the perimeter of the clamp 52to be adjacent to the needle 16.

From the foregoing it will be understood that the guidance structure isrelatively simple in form and low in mass. The stepping motors 30, 32,though not restricted in type, may for instance advantageously be of theelectromagnetic harmonic drive type disclosed in United States LettersPatent 3,331,974, issued July 18, 1967, in the name of Herbert Proctor,these motors exhibiting both a capability for precision operation athigh pulse rates and a position holding ability between steps, i.e., inthis case at the times of dwell in which the needle 16 penetrates thefabric 14. Accurate directional control of the clamp 52, or a worksupport of another design if preferred, by means of input pulses to themotors 30, 32 as above described insures that the work will bepositively fed in predetermined direction in most advantageous manner inthe available intervals between the dwells required for stitch forming,with optimum acceleration, running rate and deceleration for theparticular work. If intermittent guidance is not required as when, forinstance, continuous adhesive seaming is practiced, appropriate guidancepulsing would enable the motors 30, 32 to effect continuous guidance ofthe clamp 52 and a work piece.

While the illustrative apparatus is herein described as adapted for usein guiding a work piece having freedom in two degrees of motion it is tobe understood that in various aspects the invention is also applicableto systems wherein the work is restricted to freedom of motion in onedegree or where the work has freedom in three degrees. Moreover, theusage of two guidance units each similar to the apparatus abovedescribed and arranged adjacent one another for operation from commonelectronic controls, and respectively loaded from a common station,provides high speed production and efficiency at low cost per unit.

In operating the apparatus a work piece 14 may first be manually orotherwise located on the table 20 or the lower clamp 106 if used.Presence of the work thus located may trigger a sensor (not shown) forinitiating a series of operations including for instance: lowering thework clamp 52 onto the work 14 or W; starting the machine 12; steeringthe work on the table 20 relative to the needle 16 with the desireddirectional increments and speed changes according to the predeterminednumerical control data; and stopping the machine 12 at any desired pointwith needle up to free the work for removal. It will be understood thatthe work may optionally be advanced for peripheral or other operationsin one direction, for instance from C] as a fixed starting point on eachcollar 14 (FIG. to its point C3, or on alternate collars the work pathmay proceed instead from C3 reversely to Cl, depending on the controldata. Programming guidance for alternatively clockwise andcounterclockwise operations, for instance, eliminates so-called deadtime and can thereby keep the stitcher 12 functioning nearly 100 percentof the time in an automatic system. Also, if deemed desirable to modifystitch length from constant increments, as for example in negotiatingsharp curvature, this too may be done. Versatility of the apparatus andits relatively noncomplex electronic controls for securing exactpositions provide assurance of productivity gains in many differentfields.

The system has been described as applicable to nonrectilinear coordinatearrangement; the arcuate motion of the X-arm 40 is found to introduce nosignificant error change over a true X-Y system, affords low inertia,and is compensated for in the control logic.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

1. In an automatic work guidance mechanism for a sewing machine having arotary crankshaft and a needle cyclically operated thereby, themechanism having a member engaging the work for movement parallel andnormal to its own plane relative to the needle, a pulse generatingsynchronizer energized by the crankshaft, and means responsive to thesynchronizer pulses for providing stepping motor driving pulses, meansmounting the member for movement in substantially incremental X and Ydirections parallel to the work plane comprising:

a coordinate arm only pivotable about an axis normal to the work plane;

a first'stepping motor operatively connected to the pivotable arm by arack and pinion for swinging the arm;

a second stepping motor operatively connected to the arm by a rack andpinion and to the member for radially shifting the member relative tothe pivotal axis of the swinging arm; and

means interconnecting the stepping motors and the driving pulse meansfor driving the motors.

2. A mechanism as in claim 19 additionally comprising a second armsupporting the first stepping motor for swinging the pivotable arm.

1. In an automatic work guidance mechanism for a sewing machine having a rotary crankshaft and a needle cyclically operated thereby, the mechanism having a member engaging the work for movement parallel and normal to its own plane relative to the needle, a pulse generating synchronizer energized by the crankshaft, and means responsive to the synchronizer pulses for providing stepping motor driving pulses, means mounting the member for movement in substantially incremental X and Y directions parallel to the work plane comprising: a coordinate arm only pivotable about an axis normal to the work plane; a first stepping motor operatively connected to the pivotable arm by a rack and pinion for swinging the arm; a second stepping motor operatively connected to the arm by a rack and pinion and to the member for radially shifting the member relative to the pivotal axis of the swinging arm; and means interconnecting the stepping motors and the driving pulse means for driving the motors.
 2. A mechanism as in claim 19 additionally comprising a second arm supporting the first stepping motor for swinging the pivotable arm. 